Interbody spacer for spinal fusion

ABSTRACT

An interbody spacer for spinal fusion surgery includes first and second opposite side walls that have open-cell metal foam at upper and lower faces, and a three-dimensional lattice disposed between open-cell metal foam at the upper and lower faces. The open-cell metal foam is in communication with the three-dimensional lattice so that bone growth can enter the three-dimensional lattice from the open-cell metal foam. The interbody spacer may be formed by additive manufacturing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Ser. No. 62/412,091, filedOct. 24, 2016, the entire contents of which are incorporated herein byreference.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to an interbody spacer forspinal fusion.

BACKGROUND OF THE DISCLOSURE

Spinal fusion is a surgical procedure used to correct problems withvertebrae of the spine. Spinal fusion fuses together the painfulvertebrae so that they heal into a single, solid bone. In one method,the intervertebral disc between two vertebrae is removed and a smallinterbody spacer, also known as a cage, is inserted between thevertebrae. These interbody spacers usually contain bone graft materialto promote bone healing and facilitate the fusion. After the interbodyspacer is inserted, surgeons often use metal screws, plates, and rods tofurther stabilize the spine. Two common spinal fusion procedures areposterior lumbar interbody fusion (PLIF) and transforaminal lumbarinterbody fusion (TLIF). The type of interbody spacer is dependent onthe type of fusion procedure being performed.

SUMMARY

In one aspect, an interbody spacer for spinal fusion surgery generallycomprises first and second opposite longitudinal end portions. Alongitudinal axis of the interbody spacer extends through the first andsecond opposite end portions. First and second opposite side wallsextend longitudinally between and interconnect the first and secondlongitudinal end portions. The first and second opposite side wallsdefine a width of the interbody spacer therebetween. Upper and lowerfaces are at respective upper and lower portions of the correspondingfirst and second opposite longitudinal end portions and first and secondopposite side walls. The upper and lower faces define a height of theinterbody spacer therebetween. An interior cavity is defined by thefirst and second opposite longitudinal end portions and the first andsecond opposite side walls. The interior cavity extends through theupper and lower faces. Each of the first and second opposite side wallsincludes open-cell metal foam at the upper and lower faces, and athree-dimensional lattice disposed between the open-cell metal foam atthe upper and lower faces. The open-cell metal foam is in communicationwith the three-dimensional lattice so that bone growth can enter thethree-dimensional lattice from the open-cell metal foam.

In another aspect, a method of forming the interbody spacer set forthabove generally comprises forming the interbody spacer as a monolithic,one-piece component by additive manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of one embodiment of an interbody spacerconstructed according to the teachings of the present disclosure;

FIG. 2 is a side elevation of the interbody spacer of FIG. 1;

FIG. 3 is a top plan view of the interbody spacer of FIG. 1;

FIG. 4 is a cross section of the interbody spacer taken in the planedefined by the line 4-4 in FIG. 2;

FIG. 5 is a cross section of the interbody spacer taken in the planedefined by the line 5-5 in FIG. 3;

FIG. 6 is an enlarged view of transverse passages of the interbodyspacer as indicated in FIG. 5;

FIG. 7 is a cross section of the interbody spacer taken in the planedefined by the line 7-7 in FIG. 2;

FIG. 8 is a cross section of the interbody spacer taken in the planedefined by the line 8-8 in FIG. 7;

FIG. 9 is a perspective of another embodiment of an interbody spacerconstructed according to the teachings of the present disclosure;

FIG. 10 is another perspective of the interbody spacer of FIG. 9;

FIG. 11 is a top plan view of the interbody spacer of FIG. 9;

FIG. 12 is a longitudinal section of the interbody spacer of FIG. 9;

FIG. 13 is an enlarged view of the longitudinal section of FIG. 12;

FIG. 14 is an enlarged view of the longitudinal section of FIG. 12;

FIG. 15 is a cross section taken along the line 15-15 in FIG. 14; and

FIG. 16 is a cross section taken along the line 16-16 in FIG. 13.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE DISCLOSURE

As used herein, “open-cell metal foam” is a porous structural componenthaving a relatively roughened surface, an apparent randomized filamentarrangement, and cell sizes and shapes forming an interconnected networkor labyrinth to facilitate bone in-growth.

As used herein, a “three-dimensional lattice” is a porous structuralcomponent including non-randomized, intersecting struts forming patternsof interconnected passages to facilitate bone growth.

Referring to FIG. 1 of the drawings, a first embodiment of an interbodyspacer is generally indicated at reference numeral 10. This interbodyspacer 10 is designed for use in posterior lumbar interbody fusion(PLIF) surgery, and is referred to as a PLIF interbody spacer. The PLIFspacer 10 includes a longitudinal axis LA extending through oppositefirst and second longitudinal end portions, generally indicated at 12,14 (i.e., proximal and distal longitudinal ends); opposing first andsecond side walls, generally indicated at 16, 18 extendinglongitudinally between the first and second longitudinal ends anddefining a transverse dimension (e.g., width) of the interbody spacertherebetween; and opposite upper and lower faces, generally indicated at20, 22, defining height of the interbody spacer therebetween. Interiorsurfaces of the first and second side walls and the first and secondlongitudinal end portions define a large, interior cavity 24 extendingheightwise through the upper and lower faces generally transverse to thelongitudinal axis. The interior cavity 24 is configured to receive bonegraft material to facilitate bone growth. As used herein, terms such as“inner,” “outer,” “inward,” “outward,” “exterior,” and “interior,”relate to locations relative to the interior cavity.

The first and second longitudinal end portions 12, 14 comprise generallysolid bodies (e.g., titanium or other metal or other material) toenhance the structurally integrity (e.g., compressive strength) of thespacer at the longitudinal end portions. The illustrated first andsecond longitudinal end portions 12, 14 also comprise open-cell metalfoam 26 (e.g., titanium or other metal) on the interior surface of thesolid bodies and partially defining the interior cavity 24 to enhancebone growth. The open-cell metal foam 26 extends along the entireheights and widths of the interior surfaces of the longitudinal endportions 12, 14 (i.e., the open-cell metal foam covers entireties of theinterior surfaces of the longitudinal end portions). It is understoodthat the longitudinal end portions 12, 14 may not include the open-cellmetal foam 26 and may be of other constructions. The first longitudinalend portion 12 defines a tool-receiving opening 28 extendinglongitudinally from an exterior of the interbody spacer 10. Thetool-receiving opening 28, which may be threaded as illustrated, isconfigured to receive a suitable insertion tool for use in inserting theinterbody spacer 10 in the patient. Tool-receiving grooves 30 are formedin the first longitudinal end portion 12 on opposite sides of thetool-receiving opening 28 for receiving jaws of a suitable insertiontool. The interbody spacer 10 may include other features for use with asuitable insertion tool. The second longitudinal end 14 portion has abullet-nose shape to facilitate insertion of the interbody spacer 10 inthe patient. The second longitudinal end portion 14 may be of otherconfigurations.

The first and second side walls 16, 18 include rows of teeth 34 at theupper and lower faces 20, 22. The rows of teeth 34 extend longitudinallyadjacent the outer margins (i.e., outer perimeter) of the upper andlower faces 22, 24 relative to the central axis of the interior cavity24. That is, the first and second side walls 16, 18 are serrated at theupper and lower faces 22, 24 adjacent the outer margins of the upper andlower faces. Each tooth 34 extends in a direction generally toward thefirst longitudinal end 12. The rows of teeth 34 facilitate anchoring ofthe interbody spacer 10 to the adjacent vertebrae within the interbodyspace to inhibit movement of the interbody spacer within the space. Inother embodiments, the interbody spacer 10 may include other features tofacilitate anchoring and inhibit movement of the interbody spacer withininterbody space.

As shown in FIGS. 3 and 7, the first and second side walls 16, 18 alsoinclude open-cell metal foam 26 at the upper and lower faces 20, 22 anddisposed inward of the corresponding rows of teeth 34 (e.g.,serrations). Together with the longitudinal end portions 12, 14,open-cell metal foam 26 surrounds upper and lower edge margins of theinterior cavity 24. The open-cell metal foam 26 of the first and secondside walls 16, 18 has a depth less than the entire heights of the firstand second side walls. In other words, as shown in FIG. 7, the open-cellmetal foam 26 of the first and second side walls 16, 18 extends onlypartially along the heights of the respective first and second sidewalls from the corresponding upper and lower faces 20, 22 of theinterbody spacer 10. Overall, the open-cell metal foam 26 of the firstand second side walls 16, 18 has a width extending inward and a depthextending either from the upper face 20 toward the lower face 22 or fromthe lower face toward the upper face. Exposed surfaces of the open-cellmetal foam 26 at the upper and lower faces 20, 22 are generally rough.To inhibit the open-cell metal foam 26 from snagging on tissue, such asa nerve, during insertion of the PLIF interbody spacer 10 duringsurgery, recessed portions of the open-cell metal foam adjacent theteeth 34 are smooth (i.e., smoother) relative to the remaining portionsof the open-cell metal foam and recessed in a heigthwise directionrelative to the teeth such that the teeth extend beyond the recessedportions in the heightwise direction. The remaining portions of theopen-cell metal foam 26 inward of the recessed portions may extendbeyond the teeth 34 in the heightwise direction.

As shown in FIGS. 1, 4 and 7, each side wall 16, 18 further includes athree-dimensional lattice (i.e., 3D lattice), generally indicated at 40,disposed heightwise between the upper and lower open-cell metal foam 26and disposed longitudinally between the first and second longitudinalend portions 12, 14. Solid frames 42 surround outer portions of the 3Dlattices 40. As shown in FIG. 7, the open-cell metal foam 26 is adjacent(e.g., secured to) and inward of the interior surface of the solidframes 42 and at least partially surrounds inner portions of the 3Dlattices 40. Each 3D lattice 40 defines a plurality of intersectingpassages extending therethrough: a set of transverse passages 52extending transversely through the corresponding side wall 16, 18 fromthe interior cavity 24 through the exterior of the side wall; a set ofheightwise passages 54 extending heightwise through the 3D lattice 40from an upper end of the 3D lattice to a lower end of the 3D lattice;and a set of longitudinal passages 56 extending generally longitudinallythrough the 3D lattice from a first longitudinal end to a secondlongitudinal end of the 3D lattice. As can be seen and understood, theheightwise passages 54 are in direct communication with the open-cellmetal foam 26 at the upper and lower faces 20, 22, and all of thepassages 52, 54, 56 are in communication with and intersect one another.In this way, bone growth from vertebrae into the open-cell metal foam 26at the upper and lower faces 20, 22 can enter the 3D lattice 40 and growwithin the interconnected passages 52, 54, 56 of the 3D lattice.

In general, the open area or porosity of each 3D lattice 40 (and thuseach side wall 16, 18) increases from adjacent the exterior surface ofthe corresponding side wall toward its interior surface of thecorresponding side wall. Relatedly, the structural integrity (i.e., thecompressive strength) of each 3D lattice 40 (and thus each side wall 16,18) increases from adjacent the interior surface of the correspondingside wall toward the exterior surface of the corresponding side wallbecause there is less open area and more structure adjacent the exteriorsurface compared to the interior surface. In this way, there is moreopen area within each side wall 16, 18 for bone growth at a locationadjacent the interior cavity 24 and there is more compressive strengthto absorb compressive force adjacent the exterior surface of theinterbody spacer 10.

In the illustrated embodiment, the transverse passages 52 are arrangedin longitudinal and heightwise rows extending longitudinally andheightwise of the corresponding side wall 16, 18, respectively. A singletransverse passage 52 is shaded in FIG. 4 and another single transversepassage 52 is shaded in FIG. 7 for illustrative purposes. An enlargedtransverse passage 52 is illustrated in FIG. 8. The transverse passages52 may have the same cross-sectional shapes and cross-sectionaldimensions (e.g., cross-sectional areas), although the transversepassages may not be uniform in shape and dimensions. In the illustratedexample, each transverse passage 52 may have a generally oval or oblongcross-sectional shape, with a major axis extending heightwise and aminor axis extending longitudinally. The transverse passages 52 may haveother cross-sectional shapes. The cross-sectional area of eachtransverse passage 52 gradually increases from the exterior surface tothe interior surface such that the transverse passage generally “opensup” toward the interior surface, and tapers toward the exterior surface.In one example, the cross-sectional area of each transverse passage 52at the exterior surface may be from about 1.0 mm² to about 2.0 mm², andthe cross-sectional dimension of each transverse passage at the interiorsurface may be from about 1.5 mm² to about 2.5 mm². In one example, thecross-sectional area of each transverse passage 52 may increase by about25% to about 50% from adjacent the exterior surface to adjacent theinterior surface. As shown in FIG. 7, upper and lower transversepassages 52 are in communication with the open-cell metal foam 26 at therespective upper and lower faces 20, 22 to allow bone growth from theopen-cell metal foam to enter the transverse passages 52 and the 3Dlattice 40 in general.

In the illustrated embodiment, the heightwise passages 54 are arrangedin rows extending longitudinally and transversely along thecorresponding side wall 16, 18. A single heightwise passage 54 is shadedin FIG. 4 and another single heightwise passage is shaded in FIG. 7 forillustrative purposes. The heightwise passages 54 intersect eachtransverse passage 52 and each longitudinal passage 56 at a plurality oflocations along each of the passages. In the illustrated embodiment, thepassages 52, 54, 56 intersect each other at generally orthogonal angles.Each heightwise passage 54 may have a uniform cross-sectional dimensionalong its length. For example, as shown in FIG. 4, each heightwisepassage 54 may have a generally oval or oblong cross-sectional shape,with a major axis extending longitudinally and a minor axis extendingtransversely. The heightwise passages 54 may have other cross-sectionalshapes. As shown in FIG. 4, each heightwise passage 54 in acorresponding longitudinal row may be uniform (i.e., the samecross-sectional dimensions). As shown in FIGS. 4 and 7, the heightwisepassages 54 in a corresponding transverse row may have non-uniformcross-sectional dimensions. In particular, the cross-sectional areas ofthe heightwise passages 54 generally increase from adjacent the exteriorsurface toward the interior surface so that the cross-sectional area ofa first heightwise passage is greater than a cross-sectional area of asecond heightwise passage that is disposed outward of the firstheigthwise passage in the same transverse row. In one example, thecross-sectional areas of the heightwise passages 54 may be from about0.1 mm² to about 0.8 mm². In one example, the cross-sectional area ofthe heightwise passages 54 in the same transverse row may increase byabout 75% to about 85% from adjacent the exterior surface toward theinterior surface.

In the illustrated embodiment, the longitudinal passages 56 are arrangedin rows extending heightwise and transversely along the correspondingside wall 12, 14. A single longitudinal passage 56 is shaded in FIG. 4and another single longitudinal passage is shaded in FIG. 7 forillustrative purposes. The longitudinal passages 56 intersect thetransverse passages 52 and the heightwise passages 54 at a plurality oflocations along the passages. Each longitudinal passage 56 may have auniform cross-sectional dimension along its length. For example, eachlongitudinal passage 56 may have a generally diamond or rhombuscross-sectional shape, with a major axis extending heightwise and aminor axis extending transversely. The longitudinal passages 56 may haveother cross-sectional shapes. In the illustrated embodiment, thelongitudinal passages 56 follow the curves of the exterior and interiorsurfaces adjacent the bullet nose of the second longitudinal end portion14 so that the transverse distance of each longitudinal passage relativeto the interior and exterior surfaces is constant along the length ofthe longitudinal passage. Each longitudinal passage 56 in acorresponding heightwise row may have uniform cross-sectional shapes anddimensions (i.e., the same cross-sectional areas). The longitudinalpassages 56 in a corresponding transverse row may have non-uniformcross-sectional shapes and/or dimensions (e.g., non-uniformcross-sectional areas). In particular, as shown in FIG. 7 thecross-sectional areas of the longitudinal passages 56 generally increasefrom adjacent the exterior surface toward the interior surface so thatthe cross-sectional area of a first longitudinal passage is greater thana cross-sectional area of a second longitudinal passage that is disposedoutward of the first longitudinal passage in the same transverse row. Inone example, the cross-sectional areas of the longitudinal passages 56may be from about 0.4 mm² to about 1.0 mm². In one example, thecross-sectional areas of the longitudinal passages 56 in the sametransverse row may increase by about 250% to about 340% from adjacentthe exterior surface toward the interior surface.

In the illustrated embodiment, the 3D lattices 40 compriseinterconnected structural strut members 62. The strut members 62 areconnected to one another at nodes 68. In the illustrated embodiment,eight strut members 62 are connected at one node 68 (i.e., eight strutmembers connect to a single node). The non-randomized arrangement andconfigurations of the strut members 62 define the pattern ofintersecting passages extending through the side walls 16, 18. In theillustrated embodiment, the strut members 62 adjacent the exterior ofeach side wall 16, 18 have cross-sectional dimensions (e.g.,cross-sectional areas) greater than the cross-sectional dimensions(e.g., cross-sectional areas) of the strut members adjacent the interiorof the corresponding side wall. As shown in FIGS. 4 and 8, thecross-sectional areas of the strut members 62 may decrease graduallytoward the interior surface of the corresponding side wall 16, 18.Moreover, as also shown in FIG. 8, the strut members 62 extend fromnodes 68 at increasing angles relative to a transverse axis T passingthrough adjacent nodes and a heightwise axis H passing through adjacentnodes from adjacent the interior surface toward the exterior surface ofthe walls 16, 18. The strut members 62 also extend from nodes 68 atincreasing angles relative to a longitudinal axis passing throughadjacent nodes from adjacent the interior surface toward the exteriorsurface of the walls 16, 18. In this way, the 3D lattice 40 providesmore structural support (e.g., compressive strength) adjacent theexterior surface of the side walls 16, 18 compared to the interiorsurfaces, and the 3D lattice provides more open area adjacent theinterior surface of the side walls compared to the exterior surfaces.The 3D lattice 40 may have other configurations of strut members 62.

The interbody spacer 10 may be integrally formed as a one-piecemonolithic component. For example, the entirety of the interbody spacer10 may be formed by additive manufacturing, such as by direct metallaser sintering or by electron beam melting processes, as is generallyknown. The interbody spacer 10 may be formed entirely from a single typeof metal, such as titanium, or the interbody spacer may comprise morethan one type of metal. The interbody spacer 10 may be formed in otherways.

In use, the interior cavity 24 may be packed with bone graft materialand then inserted within an interbody space between two adjacentvertebrae in a suitable surgical procedure such that the upper face 20of the spacer 10 contacts the upper or superior vertebra and the lowerface of the spacer contacts the lower or inferior vertebra. In thisposition, the upper and lower teeth 34 anchor into the respectivesuperior and inferior vertebrae, and the open-cell metal foam 26 at theupper and lower faces 20, 22 are in close proximity and/or arecontacting the respective superior and inferior vertebrae. Afterinsertion of the spacer 10 and completion of the surgery, it isenvisioned that bone from the adjacent vertebrae will grow into theporous open-cell metal foam 26 of the first and second walls 16, 18 atthe upper and lower faces 20, 22. Further in-growth into the open-cellmetal foam 26 will lead the bone growth into the 3D lattices 40 of thefirst and second side walls 18, 20 because the open-cell metal foam isin communication with the transverse, heightwise, and longitudinalpassages 52, 54, 56 of the 3D lattice 40. Further bone growth into the3D lattice 40 will occur, particularly (it is believed) into the moreopen porous interior spaces of the first and second side walls 16, 18where the 3D lattice is more porous. It is believed such enhanced bonegrowth into the interbody spacer 10 by way of the open-cell metal foam26 and the porous 3D lattice 40 promotes bone growth of the vertebraeand enhances fusion of the patient's spine, as is desired in such fusionsurgery.

Referring to FIGS. 9-16, another embodiment of an interbody spacer isgenerally indicated at reference numeral 110. This interbody spacer 110is designed for use in transforaminal lumbar interbody fusion (TLIF)surgery, and is referred to as a TLIF interbody spacer. This TLIFinterbody spacer 110 is similar structurally to the PLIF interbodyspacer 10. As such, the TLIF spacer 110 has essentially the samestructurally elements as the PLIF spacer 10, which are indicated bycorresponding reference numerals plus 100. Differences between this TLIFinterbody spacer 110 and the PLIF interbody spacer 10 are discussedbelow.

One difference between this TLIF interbody spacer 110 and the PLIFinterbody spacer 10 is that the TLIF interbody spacer is curved alongits length, such that the first and second side walls 116, 118 havearcuate shapes along their respective lengths. The first side wall 116has a longitudinal axis that is an inner arc compared to thelongitudinal axis of the second side wall 118 such that the longitudinalaxis of the first side wall has a larger radius of curvature compared tothe longitudinal axis of the second side wall. As shown in FIG. 12, thelongitudinal passages 156 of the first and second side walls 116, 118follow the arcs or curves of the respective first and second side walls.Thus, the longitudinal axes of the longitudinal passages 156 are offsetcurves with respect to one another and with respect to the longitudinalaxis of the respective first and second side walls 116, 118. Moreover,as shown in FIG. 12, the transverse passages 152 extend along radii ofthe imaginary circles that fit the arcs of the corresponding first andsecond side walls 116, 118.

Another difference between this TLIF interbody spacer 110 and the PLIFinterbody spacer 10 is that one or more of the transverse, longitudinal,and heightwise passages 152, 154, 156 of the first side wall 116 havedifferent cross-sectional shapes and/or cross-sectional sizes (e.g.,cross-sectional areas) than the corresponding passages 152, 154, 156 ofthe second side wall 118. In particular, the cross-sectional shapes ofthe transverse (or radial) passages 152 of the first side wall 116 isgenerally diamond-shaped and have larger cross-sectional areas, whilethe cross-sectional shapes of the transverse (or radial) passages of thesecond side wall 118 is generally oval or oblong-shaped and have smallercross-sectional areas. The differences in the transverse passages 152and/or the other passages of the first and second walls 116, 118 is dueto the fact that it is believed that the first side wall, being theradially outer side wall, will take on more of a compressive load whenproperly positioned in the interbody space 110. Thus, the first sidewall 116 is designed to provide more structural support (e.g., have morecompressive strength) than the second side wall 118. Relatedly, thesecond side wall 118 will be more porous and have more percentage ofopen area than the first side wall 116.

Yet another difference between this TLIF interbody spacer 110 and thePLIF interbody spacer 10 is that the row of teeth 134 on the first sidewall 116 (the radially outer side wall) are smoother or more blunt(i.e., the edges of the teeth are less sharp or pointed) than the row ofteeth on the second side wall 118. The outer radius of the teeth 134 onthe first side wall 116 is also more rounded and less sharp than theouter radius of the teeth on the second side wall 118. These featuresfacilitate insertion of the TLIF interbody spacer 110 during the TLIFprocedure. The teeth 134 on the first side wall 116 is more likely tocome into contact with tissue (e.g., a nerve) during insertion, andtherefore, by smoothing the teeth it is less likely that the teeth withpuncture, cut and/or tear tissue during insertion.

The TLIF interbody spacer 110 may be integrally formed as a one-piecemonolithic component. For example, the entirety of the interbody spacer110 may be formed by additive manufacturing, such as by direct metallaser sintering or by electron beam melting processes, as is generallyknown. The interbody spacer 110 may be formed entirely from a singletype of metal, such as titanium, or the interbody spacer may comprisemore than one type of metal. The interbody spacer 110 may be formed inother ways.

In use, the TLIF interbody spacer 110 may be implanted in the patient ina suitable manner. It is believed the TLIF interbody spacer 110 promotesbone ingrowth in the same manner as described above with respect to thePLIF interbody spacer 10.

Modifications and variations of the disclosed embodiments are possiblewithout departing from the scope of the invention defined in theappended claims.

When introducing elements of the present invention or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

As various changes could be made in the above constructions, products,and methods without departing from the scope of the invention, it isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:
 1. An interbody spacer for spinal fusion surgery,the interbody spacer comprising: first and second opposite longitudinalend portions, wherein a longitudinal axis of the interbody spacerextends through the first and second opposite end portions; first andsecond opposite side walls extending longitudinally between andinterconnecting the first and second longitudinal end portions, whereinthe first and second opposite side walls define a width of the interbodyspacer therebetween, the first and second opposite side walls havinginterior and exterior surfaces; upper and lower faces at respectiveupper and lower portions of the corresponding first and second oppositelongitudinal end portions and first and second opposite side walls,wherein the upper and lower faces define a height of the interbodyspacer therebetween; and an interior cavity defined by the first andsecond opposite longitudinal end portions and the interior surfaces ofthe first and second opposite side walls, wherein the interior cavityextends through the upper and lower faces, wherein each of the first andsecond opposite side walls includes open-cell metal foam at the upperand lower faces, and a three-dimensional lattice disposed between theopen-cell metal foam at the upper and lower faces, wherein the open-cellmetal foam is in communication with the three-dimensional lattice sothat bone growth can enter the three-dimensional lattice from theopen-cell metal foam.
 2. The interbody spacer set forth in claim 1,wherein the three-dimensional lattice of each of the first and secondopposite side walls defines a set of transverse passages extendingtransversely through the corresponding side wall from the interiorcavity through the exterior surface of the side wall, a set ofheightwise passages extending heightwise through the three-dimensionallattice from an upper end of the three-dimensional lattice to a lowerend of the three-dimensional lattice, and a set of longitudinal passagesextending generally longitudinally through the three-dimensional latticefrom a first longitudinal end to a second longitudinal end of thethree-dimensional lattice.
 3. The interbody spacer set forth in claim 2,wherein the transverse passages, the heightwise passages, and thelongitudinal passages intersect and are in communication with oneanother.
 4. The interbody spacer set forth in claim 2, wherein an openarea of each three-dimensional lattice increases from adjacent theexterior surface of the corresponding side wall toward the interiorsurface of the corresponding side wall.
 5. The interbody spacer setforth in claim 4, wherein a structural integrity of eachthree-dimensional lattice increases from adjacent the exterior surfaceof the corresponding side wall toward the interior surface of thecorresponding side wall.
 6. The interbody spacer set forth in claim 2,wherein the transverse passages are arranged in longitudinal andheightwise rows extending longitudinally and heightwise of thecorresponding side wall.
 7. The interbody spacer set forth in claim 6,wherein a cross-sectional area of each transverse passage graduallyincreases from the exterior surface to the interior surface of thecorresponding side wall.
 8. The interbody spacer set forth in claim 2,wherein the heightwise passages are arranged in rows extendinglongitudinally and transversely along the corresponding side wall. 9.The interbody spacer set forth in claim 8, wherein a cross-sectionalarea of each heightwise passage generally increases from adjacent theexterior surface toward the interior surface of the corresponding sidewall.
 10. The interbody spacer set forth in claim 2, wherein thelongitudinal passages are arranged in rows extending heightwise andtransversely along the corresponding side wall.
 11. The interbody spacerset forth in claim 10, a cross-sectional area of each longitudinalpassage generally increases from adjacent the exterior surface towardthe interior surface of the corresponding side wall.
 12. The interbodyspacer set forth in claim 1, wherein the three-dimensional lattice ofeach of the first and second opposite side walls comprisesinterconnected structural strut members.
 13. The interbody spacer setforth in claim 12, wherein the strut members are connected to oneanother at nodes and define intersecting passages extending through theside walls.
 14. The interbody spacer set forth in claim 13, wherein thestrut members adjacent the exterior surface of each side wall havecross-sectional areas greater than the cross-sectional areas of thestrut members adjacent the interior surface of the corresponding sidewall.
 15. The interbody spacer set forth in claim 14, wherein thecross-sectional areas of the strut members decreases gradually towardthe interior surface of the corresponding side wall.
 16. The interbodyspacer set forth in claim 14, wherein strut members extend from thenodes at increasing angles relative to a transverse axis T passingthrough adjacent nodes and a heightwise axis H passing through adjacentnodes from adjacent the interior surface toward the exterior surface ofthe corresponding side wall.
 17. The interbody spacer set forth in claim14, wherein the strut members extend from the nodes at increasing anglesrelative to a longitudinal axis passing through adjacent nodes fromadjacent the interior surface toward the exterior surface of thecorresponding side wall.
 18. The interbody spacer set forth in claim 1,wherein the interbody spacer is an integrally formed, one-piececomponent formed by additive manufacturing.
 19. The interbody spacer setforth in claim 1, wherein the three-dimensional lattice of each of thefirst and second opposite side walls defines a plurality ofinterconnected passages.
 20. A method of forming an interbody spacercomprising: forming the interbody spacer as an integral, one-pieceinterbody spacer by additive manufacturing process, wherein the formedintegral, one-piece interbody spacer comprises: first and secondopposite longitudinal end portions, wherein a longitudinal axis of theinterbody spacer extends through the first and second opposite endportions; first and second opposite side walls extending longitudinallybetween and interconnecting the first and second longitudinal endportions, wherein the first and second opposite side walls define awidth of the interbody spacer therebetween, the first and secondopposite side walls having interior and exterior surfaces; upper andlower faces at respective upper and lower portions of the correspondingfirst and second opposite longitudinal end portions and first and secondopposite side walls, wherein the upper and lower faces define a heightof the interbody spacer therebetween; and an interior cavity defined bythe first and second opposite longitudinal end portions and the interiorsurfaces of the first and second opposite side walls, wherein theinterior cavity extends through the upper and lower faces, wherein eachof the first and second opposite side walls includes open-cell metalfoam at the upper and lower faces, and a three-dimensional latticedisposed between the open-cell metal foam at the upper and lower faces,wherein the open-cell metal foam is in communication with thethree-dimensional lattice so that bone growth can enter thethree-dimensional lattice from the open-cell metal foam.